The present invention relates to a process for increasing the molecular weight of an amide ester polymer.
U.S. Pat. No. 6,172,167 discloses amide ester polymers having good mechanical and environmental properties. The polymers of the '167 patent consist of building blocks with the general structure -(CB-VB)- wherein CB represents a block of constant length and VB represents a block of variable length. When the number average molecular weight of the polymer composition of the '167 patent is greater than 10,000 grams per mole, then the polymer compositions have increased strength, stiffness, elasticity and ductility properties and display improved film and fiber forming properties. The process of the '167 patent produces higher molecular weight polymers by heating the polymer to promote chain condensation. However, the rate of such chain condensation slows significantly as the molecular weight of the polymer increases. Therefore, it is time consuming to produce the desirable high molecular weight polymers using the process of the '167 patent. Thus, there remains a need for a more facile method to produce increased molecular weight amide ester polymers of this type.
Alternatively it may be desirable to either increase the molecular or to produced branched high molecular weight crystallizable polyester-amides by using polyfunctional initiators but avoiding gelation of the composition.